Layer 7 load balancing
Both public and private application load balancers support layer 7 load balancing. Data traffic is distributed based on configured policies and rules. A policy defines the action to take, which means how the traffic is distributed, when the incoming request matches the rules that are associated with the policy.
Policies
You can define policies for HTTP and HTTPS listeners. For each policy, you must define one or more rules. The policy is applied only when all its rules are matched.
You can attach more than one policy to a listener. In general, a policy with the lowest priority is evaluated first. Each policy must have a different priority.
If the incoming request does not match the rules for any policy, the system request redirects to the configured HTTPS redirect listener, if present. Otherwise, the system redirects the request to the default pool of the listener. The HTTPS redirect has a higher precedence over the default pool on an HTTP listener.
The following actions are supported for a layer 7 policy:
- Reject - The request is denied with a 403 response.
- Redirect - The request is redirected to a configured URL and response code.
- Forward - The request is sent to a specific back-end pool.
- HTTPS Redirect - The HTTP request redirects to an HTTPS listener.
Policy properties
| Property | Description |
|---|---|
| Name | The name of the policy. The name must be unique within the listener. |
| Action | The action to take when all policy rules match. The acceptable values are reject, redirect, forward, and https_redirect. |
| Priority | Policies are evaluated based on ascending order of priority. |
| URL | The URL to which the request is redirected, if the action is set to redirect. |
| HTTP status code | Status code of the response returned by the application load balancer when the action is set to redirect or https_redirect. The acceptable values are: 301, 302, 303, 307,
or 308. |
| Target | The back-end pool of virtual server instances to which the request is forwarded, if the action is set to forward. |
| Listener | The HTTPS listener to which the request is redirected, if the action is set to https_redirect. |
| URI | The relative URI to which the request is redirected, if the action is https_redirect. This property is optional. |
Rules
A layer 7 rule defines how a request is to be matched. Both URI-based routing and parameter-based routing are supported. Five types of rules are supported, described in Table 2.
| Type | Description |
|---|---|
hostname |
The request matches the specified hostname, such as api.my_company.com. |
header |
The request matches an HTTP header field and value, such as Cookie: xxxx. |
path |
The request matches the path in the URL after the hostname, such as /index.html. |
query |
The request matches the query in the URL, for example x=y. The query string must be percent-encoded, and it is case-sensitive. |
body |
If the request body of the POST request is form encoding. The request matches the body, for example key=value. It is case-sensitive. |
To match a request, a condition statement must be defined in a rule. Three conditions are supported, described in Table 3.
| Condition | Type of evaluation |
|---|---|
contains |
Verify whether the value extracted based on the type contains the string that is specified in the value. |
equals |
Verify whether the value extracted based on the type is identical to the string specified in the value. |
matches_regex |
Match the value extracted based on the type with the regular expression that is specified in the value. |
Rule properties
Table 4 describes layer 7 policy rule properties.
| Property | Description |
|---|---|
type |
Specifies the type of rule. The acceptable values are hostname, header, path, query, or body. |
condition |
Specifies the condition with which a rule is evaluated. Condition can be: contains, equals, or matches_regex. |
field |
Specifies the field name. This field is applicable only to the header query and body rule type and does not support regular expression and wildcard characters. For example, to match a cookie in the
HTTP header, the field can be set to cookie. When the rule type is query and body, this field is optional. |
value |
The string to be matched. Does not support wildcard characters. Supports regular expression if the condition is set to matches_regex. |
Notes:
- If the rule type is
header, the following characters are not allowed forfieldandvalue:"(),/:;<=>?@[\]{}'. - If the rule type is
body, the following characters are not allowed forfieldandvalue:"'=,()&and space. - If the rule type is
query,fieldandvaluemust be a percent-encoded string.
Examples: Creating policies and rules
The following layer 7 examples show how policies and rules are created and associated with a listener.
Example 1: Create an HTTPS listener with redirect policies
curl -H "Authorization: $iam_token" -X POST
"$vpc_api_endpoint/v1/load_balancers/$lbId/listeners" \
-d '{
"certificate_instance": {
"crn": "crn:v1:bluemix:public:cloudcerts:us-south:a/1111111111111111111111111111:22222222-3333-4444-5555-666666666666:certificate:77777777777777777777777777777777"
},
"connection_limit": 2000,
"port": 443,
"protocol": "https",
"policies": [
{
"name": "hostname_header",
"action": "redirect",
"priority": 1,
"target": {
"url": "https://www.examples.com/",
"http_status_code": 307
},
"rules": [
{
"condition": "contains",
"type": "header",
"field": "aheader",
"value": "avalue"
},
{
"condition": "equals",
"type": "hostname",
"value": "abc.com"
}
]
},
{
"name": "header_cookie",
"action": "redirect",
"priority": 5,
"target": {
"url": "https://www.mycookies.com/",
"http_status_code": 302
},
"rules": [
{
"condition": "contains",
"type": "header",
"field": "aheader",
"value": "avalue"
},
{
"condition": "equals",
"type": "header",
"field": "cookie",
"value": "flavor=oatmeal"
}
]
},
{
"name": "path_hostname",
"action": "redirect",
"priority": 10,
"target": {
"url": "https://www.myexamples.com/",
"http_status_code": 301
},
"rules": [
{
"condition": "contains",
"type": "hostname",
"value": "abc"
},
{
"condition": "equals",
"value": "/test",
"type": "path"
}
]
}
]
}'
Example 2: Create policies to forward requests to pools and associate it with an existing listener
curl -H "Authorization: $iam_token" -X POST
"$vpc_api_endpoint/v1/load_balancers/$lbId/listeners/$listenerId/policies" \
-d '{
"policies": [
{
"action": "forward",
"priority": 1,
"target": {
"id": "7df616da-4dd6-43d3-881d-801ae29e29fe"
},
"rules": [
{
"condition": "equals",
"type": "header",
"field": "cookie",
"value": "flavor=oatmeal"
}
]
},
{
"action": "forward",
"priority": 5,
"target": {
"id": "0738-8061c411-0d50-4c79-b475-102666796434"
},
"rules": [
{
"condition": "contains",
"type": "header",
"field": "aheader",
"value": "avalue"
}
]
},
{
"action": "forward",
"priority": 10,
"target": {
"id": "0738-62914e09-3928-4d89-b7f7-1bb7a6d7fe85"
},
"rules": [
{
"condition": "matches_regex",
"type": "hostname",
"value": "abc[a-z]*.com"
}
]
},
{
"action": "forward",
"priority": 6,
"target": {
"id": "0738-62914e09-3928-4d89-b7f7-1bb7a6d7fe85"
},
"rules": [
{
"condition": "equals",
"type": "path",
"value": "/test/testtest"
}
]
}
]
}'
Example 3: Create an HTTP listener with https redirect policies
curl -H "Authorization: $iam_token" -X POST
"$vpc_api_endpoint/v1/load_balancers/$lbId/listeners" \
-d '{
"connection_limit": 2000,
"port": 80,
"protocol": "http",
"policies": [
{
"name": "hostname_header",
"action": "https_redirect",
"priority": 1,
"target": {
"listener": {
"id": "0134-d578be10-31e3-46b3-8513-79babb852319"
},
"http_status_code": 307
},
"rules": [
{
"condition": "contains",
"type": "header",
"field": "aheader",
"value": "avalue"
},
{
"condition": "equals",
"type": "hostname",
"value": "abc.com"
}
]
},
{
"name": "header_cookie",
"action": "https_redirect",
"priority": 2,
"target": {
"listener": {
"id": "0456-a578be10-31e3-46b3-8513-79babb852398"
},
"http_status_code": 302
},
"rules": [
{
"condition": "contains",
"type": "header",
"field": "aheader",
"value": "avalue"
},
{
"condition": "equals",
"type": "header",
"field": "cookie",
"value": "flavor=oatmeal"
}
]
},
{
"name": "path_hostname",
"action": "https_redirect",
"priority": 5,
"target": {
"listener": {
"id": "0386-d898be10-21e3-66b3-9513-69babb852390"
},
"http_status_code": 301,
"uri": "/test/sample"
},
"rules": [
{
"condition": "contains",
"type": "hostname",
"value": "abc"
},
{
"condition": "equals",
"value": "/test",
"type": "path"
}
]
}
]
}'